The Ways of the Orchids. 389 



The pollen masses with their appendages are collectively 

 called Pollinia, a word which we shall have occasion to use. 

 The orchids are botanically considered to have " three united 

 pistils or female organs." The two lower stigmas* are often 

 confluent, so as to appear as one. The upper pistil exists in a 

 very modified and curious condition, having its stigma con- 

 verted into the 'Rostellum, of which it is very difficult to give 

 an intelligible description without the aid of a drawing, which 

 time will not allow us to prepare. Mr. Darwin observes : " the 

 rostellum is a nearly spherical, somewhat pointed projection, 

 overhanging the two almost confluent stigmas." It either 

 includes, or is formed of viscid matter, and has two discs to 

 which the pollen masses are attached by means of their caudicles. 

 These organs, as we shall see, have a most important work to 

 perform, and they may be discovered in any common orchid, 

 by removing the sepals, or leaves of the calyx, and the petals or 

 flower leaves, except the lowest, which has the most singular 

 shape, and is called the labellum, or lower lip. This lip forms 

 a convenient landing-place for insects, " it secretes nectar, in 

 order to attract them, and is often produced into a long spur- 

 like nectary." If an insect alights on the lip, and tries to 

 reach the nectary with his proboscis, it finds the rostellum in 

 the way, and in pushing by it detaches one or more of the 

 viscid discs to which the pollen masses are attached. Mr. 

 Darwin succeeded in imitating this action by introducing a 

 pointed pencil, and on drawing it back the disc was firmly 

 attached. While these discs are in their place a liquid keeps 

 their cement moist, but when they are removed it sets in a 

 few minutes, and causes the pollen masses to be firmly fixed to 

 the intruding body. This is essential to the process of fertiliza- 

 tion, for if it slipped on one side or the other it would not come 

 into contact with the right portion of the pistil of the flower to 

 which the insect paid its next visit. Nor would it succeed if it 

 preserved the upright attitude in which the adhesion took place. 

 Let the reader hold a finger upright, and suppose the pollen 

 mass attached to its tip, let him then curve the finger hori- 

 zontally—that is the position which the anther must attain. This 

 change is effected in about half a minute, by the contraction of 

 the adhesive disc. Thus, while an insect flies from one flower 

 to another, this highly curious apparatus arranges itself exactly 

 in the right direction for its work. Now comes another in- 

 teresting adaptation, noticed long ago by Robert Brown. The 

 stigma or pistil head is very sticky, but not so tenacious as to 

 pull off all the pollen after a single contact. Its resistance to 

 an insect's return snaps some of the threads by which the 



* The stigma is the fleshy extremity of the pistil, and may be seated upon the 

 ovary, or elevated upon a stalk — the style. 



VOL. I. — NO. V. DD 



